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Basic Algebra/Introduction to Basic Algebra Ideas/Variables and Expressions

VocabularyEdit

Variable
Term
Operation
Expression
Evaluate
Substitute

LessonEdit

A variable is a letter or symbol that takes place of a number in Algebra. Common symbols used are  ,  ,  ,   and  . The letters x and y are commonly used, but remember that any other symbols would work just as well.

Variables are used in algebra as placeholders for unknown numbers. If you see "3 + x", don't panic! All this means is that we are adding a number who's value we don't yet know.

Some examples of variables in use:

  •   -- three times of  .
  •   -- five minus  
  •   or  -- 2 divided by  

A term is a number or a variable or a cluster of numbers and variables multiplied and or divided separated by addition and subtraction.

Examples of terms:

  •   The terms are 3 and 5.
  •   The term is  , 6 over   is one term, because the operation is division.
  •   The terms are 6  and 5, 6  and 5 are separate terms because they are separated by a addition or subtraction.

An operation is a thing you do to numbers, like add, subtract, multiply, or divide. You use signs like +, , *, or / for operations.

An expression is two or more terms, with operations between all terms.

Examples of expressions:

  •  
  •  
  •  
  •  

To evaluate an expression, you do the operations to the terms of an expression.

Examples of evaluating expressions:

  •   evaluates to 7.
  •   evaluates to 6.
  •   evaluates to 17.


To evaluate an expression with variables, you substitute (put a thing in the place of an other thing) numbers for the variables.

Examples of substituting: (Substitute 3 for x in these examples.)

  •   is  .
  •   is  .
  •   is  .

Example ProblemsEdit

Evaluate the following expressions

  •  
When  
 
Substitute 2 for  .
 
Evaluate   to get the answer.
  •  
When   and  
 
Substitute 9 for   and substitute 4 for  .
 
Evaluate   to get the answer.

Practice GamesEdit

Practice ProblemsEdit

remember order of operations

Evaluate each expression if   = 1,   = 2,   = 3, and   = 5.

1

 

2

 

3

 

4

 

5

 

6

 

7

 

8

 

Evaluate each expression if   = 4,   = 2, and   = 3.

9

 

10

 

11

 

12

 

13

 

14

 

15

 

16

 

More harder questions: Evaluate each expression if   = 5,   = 8, and   = 9.

17

 

18

 

19

 

20

 

21

 


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Variables and Expressions
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Order of Operations Working With Negative Numbers